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Add output_length parameter to mbedtls_gcm_finish

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Without this parameter, it would be hard for callers to know how many bytes
of output the function wrote into the output buffer. It would be possible,
since the cumulated output must have the same length as the cumulated input,
but it would be cumbersome for the caller to keep track.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
This commit is contained in:
Gilles Peskine
2021-06-23 21:51:32 +02:00
parent f06b92d724
commit 5a7be10419
4 changed files with 31 additions and 9 deletions
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13
library/cipher.c
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@ -1109,9 +1109,14 @@ int mbedtls_cipher_write_tag( mbedtls_cipher_context_t *ctx,
#if defined(MBEDTLS_GCM_C)
if( MBEDTLS_MODE_GCM == ctx->cipher_info->mode )
{
size_t output_length;
/* The code here doesn't yet support alternative implementations
* that can delay up to a block of output. */
return( mbedtls_gcm_finish( (mbedtls_gcm_context *) ctx->cipher_ctx,
NULL, 0,
NULL, 0, &output_length,
tag, tag_len ) );
}
#endif
#if defined(MBEDTLS_CHACHAPOLY_C)
@ -1158,12 +1163,16 @@ int mbedtls_cipher_check_tag( mbedtls_cipher_context_t *ctx,
#if defined(MBEDTLS_GCM_C)
if( MBEDTLS_MODE_GCM == ctx->cipher_info->mode )
{
size_t output_length;
/* The code here doesn't yet support alternative implementations
* that can delay up to a block of output. */
if( tag_len > sizeof( check_tag ) )
return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
if( 0 != ( ret = mbedtls_gcm_finish(
(mbedtls_gcm_context *) ctx->cipher_ctx,
NULL, 0,
NULL, 0, &output_length,
check_tag, tag_len ) ) )
{
return( ret );